
%0 Journal Article
%A Sattel, Daniel 
%A Battig, Eric 
%T Square-wave processing of MEGATEM data
%J ASEG Extended Abstracts
%D 2018/02/26
%V 2018
%N 1
%P 1-5
%K 
%R https://doi.org/10.1071/ASEG2018ABP044
%U https://www.publish.csiro.au/paper/ASEG2018ABP044 
%X The recording of raw or streamed EM survey data, as done by CGG during MEGATEM surveys, allows for the reprocessing of the acquired EM data, including square-wave processing. During the latter, the recorded EM response to the actual half-sine waveform is replaced by the EM response to a square-wave, derived via deconvolution/convolution in the frequency domain. This makes the on- and early-time information more accessible for data modelling, including 1D inversions and conductivity-depth transformations. Square-wave EM data can also be corrected for survey height, transmitter-receiver offset and transmitter attitude. That correction allows for the interpretation of early-time EM response grids, which generally offer better spatial resolution than derived conductivity-depth slices. The advantages of square-wave processing are demonstrated on a MEGATEM data set acquired in 2013 in South America. With survey terrain clearance ranging from 100 &#x2013; 1600 m, due to the rugged topography, early-time grids of elevation-corrected square-wave data outlined the shallow conductivity structure, whereas early-time grids of the original half-sine data mostly reflected the variable system elevation. Further, derived conductivity-depth sections of the square-wave data show more lateral continuity than the sections derived from the original half-sine data. These results show that the early-time information of square-wave is more accessible than in the original data, facilitating interpretation of shallow conductivity structures. 
